Process of synthesizing methane from gases



l 60 various ways.

Patented Aug. 12, 1930 PATENT OFFICE ALFRED H. WHITE, ANN ARBOR, MICHIGAN PROCESS OF SYNTHESIZING METEANE FROM GAQES I We Drawing.

This invention relates to a process of synthesizing methane from gases containing carbon monoxide and hydrogen, and more particularly to a process wherein such gases are a contacted at an elevated temperature with solid material capable of facilitating the reaction whereby methane is formed.

This invention is useful in increasin the unit heating value and improving the ame 1c characteristics of man industrial gases containing carbon monoxide and hydrogen, and

for illustrative purposes, I describe its ap li-;

cation to bluewater gas as one example 9 an industrial gas suitable for the synthesls of 1 methane in accordance with the process of my invention,

Blue water as consists-mainly of carbon monoxide and iydrogen with lesser amounts of carbon dioxide and nitrogen and small at amounts of sulphur compounds and hydrocarbons. The crude hot his water gas frequently contains a rather large percentage of steam in addition to the constituents mentioned. This blue water gas has a heating Q5 value of about 300 British thermal units er cubic foot and is, therefore, unsuited for istribution as cit gas where'the heating value must usually e over 500 British thermal units per cubic foot.

ac Various attempts have been made to convert the constituents of the blue water as to methane and among other instances may cite British Patent 12,461 issued in 1902 to Elworthy, and \Villiamson, and French Patcut 355,900 issued to Sebatier in 1905. Both of these inventors assed a mixture of carbon monoxide and by rogen over a nickel catalyst at temperatures of 250 to 500 C. Various equations may be written to express the 4 possible reactions which take place between the hydrogen, carbon monoxide, carbon dioxide and water vapor of the blue water gas but the following reaction is accepted as one of the principal ones.

Application filed October 5, 1925. Serial No. 60,684.

completely. After the oxide which orms the base of the active mass has become converted to carbonate, it may be regenerated by heating to a temperature high enough to dissoci= ate the carbonate and regenerate the oxide, when, after reduction of nickel oxide formed, the catalyst is again ready for use and absorption of CO as before.

As an example of the manufacture of a catalyst suitable for my process, I set forth the following description: About 52 parts of a calcined magnesite are intimately mixed, in the dry state, with about 11 parts of a binder such as clay kaolin, cement, etc., and to this pulverized mixture is added a solution of 13 parts of nickel nitrate in 24 parts of water. After thoroughly mixing and working these materials, I obtain a semiplastic mass which may be formed into any desired shapeas pellets, briquets, cubes, and the likewhich may then be dried and heated to a temperature suflicient to decompose the magnesium carbonate contained therein, and may be treated in any convenient manner, such as heating in a current of hydrogen gas or in a gaseous mixture of carbon monoxide and hydrogen, whereby reduction of the nickel nitrate to metallic nickel is effected.

I do not wish to restrict my rocess to any particular type of ap aratus. lt may be carried out in any suita le apparatus in which is provided (1) a chamber, or chambers, for containing and heating the oxide-catalyst, through which a gaseous mixture containing carbon monoxide and hydro en may be passed so as to bring the gas Into intimate contact with the heated catalyst. There may be provided a condenser or heat interchanger or other device for lowering the temperature of the gaseous mixture leaving the nickel nitrate, dry, ignite, and

- same as that at which the catalyst is mainlast of the catalyst-containing chambers so as tocremove a art, at least, 0 the water var contained t erein, and further there ma rovided (3) suitable equipment for co lectlng, holding and storing the gaseous products derived from my rocess.

In citing a typical examp e of the mode of operation of my process, it is understood that I do not restrict myself to the set of conditions stated inasmuch as my process enables operations to be carried out under a diversity of conditions of temperature, pressure, rate of as flow, etc.

(gne typical mode of operation of the process heretofore described is:

The aseous mixture, containing carbon monoxi e and hydrogen, which may be -preheated to a temperature approximately the tained is led into the chamber containing the reduced, decarbonated catalyst material and the gases passed into intimate contact with the catalyst heated to a temperature which is favorable to the formation of methane and carbon dioxide and atwhich carbon dioxide reacts with the decarbonated catalyst to con vert the oxide into a carbonate. These temperatures lie within the range of 450 F. to 1400 F. The particular temperature within this general range at which the catalyst is maintained will vary for different catalysts, different gas compositions, etc. For example, the tem erature at which calcium carbonate isstablle' when in contact w1th a gas containing a iven concentration of carbon dioxide is we lknown, and in operating with a catalyst containing calcium oxide the temperature employed will be one within the above range (450 F. to 1400 F.) fillWhlCh calcium carbonate is stable under the other conditions of operation. In general, I have found that a calcium oxide catal 'st may be used to advantage at about 750 The rate of flow of the gases may be varied within wide limits, so as to give any desired length of time for contact between gases and catalyst. The gases may be passed through the catalyst under positivepressure, that is be forced in or blown into the chamber containing the catalystybut it is understood that my,

process may advantageously be carried out at approximately atmospheric pressure or apressure only slightly above atmospheric.

. Following its assage thru one or more chambers containing the'heated catalyst the gaseous products are removed from the system, being collected and stored in any convenient manner, or if desired the gaseous products may be mixed with the original gas containing carbon monoxide and hydrogen and a ain passed over the heated catalyst until t e degree of enrichment deemed favorable has been secured.

I further state that, as an example of my treatment of spent or carbonated catalyst,

of the carbonate is virtually complete, e.

carbonates and drive off 00,.

the following mode of procedure is typical though'I do not wish to restrict the process exclusivel to operations described.

After t e catalyst material has been used as set forth above, in converting carbon monoxide-to methane and carbon dioxide, and has absorbed a considerable amount of the carbon dioxide formed, the catal st may be heated to a temperature at which dissociation for the catalyst described in an exam above, a temperature of 960 to 1100 while a current of air, or a current of othergases 1s passed over it. The catalyst may then be reduced by heating in a current of hydrogen, or in a gaseous mixture containing hydrogen, or carbon monoxide, or both, at a temperature below 750 F. as during the manufacture of catalytic material described above.

As a further illustration of how my invention may be applied, the following method of operation may be used in connection with a water gas gmt of the usual present construction. 0 additional chambers for methane conversion are added to the present series of three, which latter series consists of carburetor, enerator and su rheater. These new cham ers are to be fille with the oxide mass and connected in parallel after the superheater. During the process of blasting, the blast gases leaving the superheater are passed through the No. 1 methane converter to heat it hot enough to dissociate the This No. 1 methane converter will now be hotter than desirable for synthesis of methane and will be cooled, preferably with the help of a stream of cooler gas or steam, while the No. 2 methane converter is in operation, formin jnethane from the blue gas made in the su sequent run in. the usual c cle. During the next blasting process, the o. 2 converter will be heated to decompose the carbonate, and the No. 1 converter will be used to synthesize methane during the following run.

In this way the two converters are used al-.

terflately, and the raw blue gas is converted into methane withoutauxihary coolers or heat interchan ers.

Although I ave cited the use of nickel as a catalyst, other catalysts, which will promote the s nthesis of methane, may be, of course, use and although I have cited lime and magnesia as the .base on which the cata- I do not restrict myself to this method of operation.

Methane is the principal hydrocarbon formed by this method of synthesis by ethylamaeea ene, ethane and perhaps other hydrocarbons are formed in minor amounts.

The use of an oxide such as lime or magnesia is also useful in protecting the catalyst from poisonous effects of compounds of sulphur which by preference react with the lime or magnesia rather than with the catalyst. Even if the catalyst is poisoned in the la ers of oxide which first come in contact wlth the impure gas, the sulphur compounds will'be removed from'the gas by these first layers of oxide and combined as solid sulphur-containing compounds, and the bulk of the catalyst will be protected and remain active. These solid sulphur compounds will be decomposed during the regeneration of the oxides, preferably with the aid of a stream of carbon dioxide, steam, or h drogen passing through the mass and both the catalyst and oxides will thereby be freed of poisonous sulphur compounds and will again become active.

A catalyst is useful in accelerating the rate of reaction, but the presence of lime, magnesia, or other oxides capable of forming carbonate at the temperature of the formation of methane, will promote the synthesis of methane, since it removes the carbon dioxide from the gas base as soon as it is formed, and I may, there ore, use such oxides or a mixture of oxides, without any other catalyst, to-promote the reaction.

An added advantage in my process is due to the heat-evolved when the carbon dioxide formed simultaneously with the methane reacts with the oxide to form carbonate. This heat of reaction prevents the convrter from cooling off during the synthesis of methane and even allows the use of a gas entering the methane converter at a lower temperature than is otherwise practicable for a desirable rate of formation of methane. v

The reaction which I have cited between carbon monoxide and hydro en is the principal one which occurs w en methane is formed from blue water gas. However, there are other well known reactions between carbonand steam and between carbon monoxide and steam which will also give methane, and I desire to include these also as within the scope of my process. As instances of these reactions, I may cite: 1

400 2H OSCH 3002 2C 2H OSCH CO:

ing to my process, the equation becomes:

20 l 080508.603 CH4 If this reaction proceeds completely to the right 48,450 calories of heat are evolved for each gram molecule of methai ie formed while without the lime, only 8,580 calories of heat are. evolved.

The as does not have to be freed from suspen ed carbon hydrocarbons, or sulphur com unds, for even if the catalytic material comes coated with carbon and fouled by sulphur compounds, both of these materials Wlll be removed during the regeneration of the oxides.

Although I have discussed mainly the aplication of my process to blue water gas, it 1s evident that it may also be ap lied to any industrial gas which contains cai li ide and hydrogen, or carbon monoxide and steam, such as, producer or coke oven gas. Blast furnace gas which consists mainly of carbon monoxlde and nitrogen ma have steam added to it and then be treate by my process. T

It will be obvious that various changes may be made in the practising of my invention without departing from the spirit thereof and it is my intention to cover by m claims such changes as may be included wit in the scope of m invention.

atIclaimis:'

1. The process of synthesizing methane from a mixture of gases containlng carbon monoxide and hydrogen, which comprises contacting at a temperature above 450 F. and below 1400 F. said mixture of gases with a material comprising nickel distributed on solid masses consisting largely of mag nesium oxide.

2. The process of synthesizing from a mixture of gases containing carbon monoxide and hydrogen, which comprises contacting at a temperature above 450 F. and below 1400 F. said mixture of gases with nickel distributed on solid masses consisting largely of magnesium oxide, whereby methane is formed and said oxide forms a carbonate material, then raising the temperon monoxmethane ios 3. The process of synthesizing methane I from a mixture of gases containing carbon monoxide, hydrogerr, and sulfur compounds, which comprises contacting at a temperature above 450 F. and below 1400 F. said mixture of gases with nickel distributed on solid masses consisting largely of magnesium oxide whereby to formcarbonates and sulfides.

4. The process of synthesizing methane from a mixture of gases containing carbon monoxide, hydrogen, and sulfurcompounds, which comprises contacting at a temperature [ill above 450 F. and below 1400 F. said mixture of gases with nickel distributed on solid masses consisting largely of magnesium oxide, whereby methane is formed and said oxide forms a carbonate and sulfide, then raising the temperature of thesolid masses containing carbonate and sulfide to a temperature at which said carbonate and sulfide dissociate and the oxide is regenerated, then lowering the temperature to a point where the oxide is again capable of forming carbonate and sulfide and synthesizin methane from a gaseous mixture containing hydrogen, carbon monoxide, and sulfur compounds, as in the first instance.

5. The process of preparing a methane containing as from combustible ases containing oxi es of carbon and hydrogen which consists in causing the gases to contact with a nickel catalyst supported on a base composed mainly of magnesium oxide at tempertures between 450 and 1100 F. and "to react in contact with this catalyst until at least one-quarter of the carbon initially present as oxide shall have been converted to methane.

ALFRED H. WHITE. 

